With the requirement on low-carbon protection in modern society, the power battery tends to be used more and more widely, and the most notable feature of the power battery in the fields of electric vehicles and energy storage power station lies in modularized assembling, that is, a battery module is assembled by a plurality of mono-batteries (as shown in FIG. 1), then a plurality of battery modules are connected in series and/or in parallel and received in a case so as to form a battery pack. A bonding material (not shown) is typically applied on both end surfaces 11 of each mono-battery 1, then the plurality of mono-batteries 1 and two end plates 2 are bonded together in an arrangement manner as shown in FIG. 1, so as to provide a larger bonding area. In each mono-battery 1, because the surface area of each of the two end surfaces 11 is the largest, the bonding area is the largest when the bonding material is applied on the end surface 11. However, since the plurality of mono-batteries 1 are arranged sequentially and closely adjacent to each other, there is no space to buffer swelling of any one mono-battery 1; since each mono-battery 1 will generate different extent of swelling during charging and discharging, a large load will be generated and applied to a frame (the frame is formed by the two end plates 2 and two side plates 3) due to the swelling of all the mono-batteries 1, and the frame will be deformed and in turn will fail, so such a configuration is not suitable for the design of the battery module in a situation that the mono-battery 1 swells seriously. Meanwhile the load from all the mono-batteries 1 will be finally applied to the two end plates 2 via the two bonding materials which are respectively positioned between the two mono-batteries 1 and the two end plates 2, and in turn will be transferred to the other battery modules of the battery pack via these two end plates 2. In order to maintain the secure bonding between all the mono-batteries 1 and the two end plates 2 and in turn maintain the structure stability of the frame of the battery module, the requirement on bonding strength of the adhesive of the bonding material used for each battery module is very high, and the requirement on structure strength of the frame of the battery module is also very high. The structural design is not suitable for the design that the battery module works in severe condition (for example, the battery module will bear a higher impact load or a long time vibration load for the electric vehicle) and the number of the mono-batteries 1 is large. At the same time, a bottom plate 4 is not directly connected with the other metal components (the end plates 2 and the side plates 3) of the battery module, so all the metal components of the battery module do not have an equipotential design, and in turn the equipotential design must be later designed for the battery pack, which is not convenient in the design of the battery pack.